Anticancer drug-chitosan complex forming self-aggregates and preparation method thereof

ABSTRACT

The present invention relates to an anticancer drug-chitosan complex forming self-aggregates and the preparation method thereof. More precisely, the present invention relates to the anticancer drug-chitosan complex forming self-aggregates in aqueous media composed of a hydrophobic anticancer agent and a hydrophilic chitosan, and the preparation method thereof. The anticancer drug-chitosan complex of the present invention not only works selectively against target tumor tissue but also continues to release the medicine over a long period of time. Besides, the anticancer drug-chitosan complex could have greater amount of drug by adding the anticancer drug into self-aggregates, which is generally limited by chemical bond. Therefore, the anticancer drug-chitosan complex of the present invention can be effectively used for the cancer chemotherapy.

FIELD OF THE INVENTION

The present invention relates to an anticancer drug-chitosan complexforming self-aggregates and the preparation method thereof. Moreprecisely, the present invention relates to the anticancer drug-chitosancomplex forming self-aggregates in aqueous media composed of ahydrophobic anticancer agent and a hydrophilic chitosan, and thepreparation method thereof. The anticancer drug-chitosan complex of thepresent invention not only works selectively against target tumor tissuebut also continues to release the medicine over a long period of time.Besides, the anticancer drug-chitosan complex could have greater amountof drug by adding the anticancer drug into self-aggregates, which isgenerally limited by chemical bond. Therefore, the anticancerdrug-chitosan complex of the present invention can be effectively usedfor the cancer chemotherapy.

BACKGROUND

Anticancer chemotherapy was set about progressing as choriocarcinoma wascured completely by using methotrexate. As of today, about 50 differentkinds of anticancer drugs have been used and especially,choriocarcinoma, leukemia, Wilms' tumor, Ewing's sarcoma, rhabdomyoma,retinoblastoma, lymphoma, mycosis fungoides, testis tumor et cetera havebeen satisfactorily treated with those anticancer drugs.

Recently, knowledge about the development of cancer and thecharacteristics of tumor cells has been disclosed a lot and studiesconcerning the development of new anticancer drugs have followed. Mostanticancer drugs show anticancer effect by suppressing the synthesis ofnucleic acid of tumor cells or defunctioning the nucleic acid bydirectly combining with the nucleic acid. However, they have seriousside effects such as bone marrow depression, gastrointestinal damage andlose hair since these anticancer drugs work not only tumor cells butalso for normal cells.

The biggest problem of using anticancer drugs is that those drugs do notselectively work for only tumor cells. That is; anticancer drugs areworking for every cells showing fast division or proliferation (bonemarrow cells, epitherial cells of stomach and intestines, hair folliclecells, etc.), causing almost every cancer patients to be suffering fromside effects such as bone marrow depression, gastrointestinal trouble,and lose hair, etc. Nevertheless, the anticancer drugs have therapeuticeffect against cancer because tumor cells respond more sensitively thannormal cells, so that more tumor cells are destroyed than normal cells,in addition, normal cells are regenerated faster than tumor cells.Meanwhile, besides the anticancer effect, those anticancer drugs alsohave anti-immune effect. Thus, it is another use of anticancer drugs tobe provided to patients who need organ transplantation for the purposeof eliminating rejection symptoms after transplantation. But the dangerof infection should be considered for cancer patients since those drugsdrop immunity.

About 50 anticancer drugs have been widely used so far. These drugs areclassified according to their reaction mechanism and components. Amongthem, adriamycin, commonly called doxorubicin, is highly effective forthe treatment of malignant lymphoma, acute myeloid leukemia, soft tissueosteosarcoma, breast cancer, ovarian cancer, lung cancer, bronchialcancer, bladder cancer, digestive system cancer, etc. Although it is avery effective anticancer drug, it still presents such side effects assevere bone marrow depression, hypofunction of heart and kidney, andoutflow of blood from blood vessels into tissues (N. Eng. J. Med., 1981,305, 139).

Cancer chemotherapy is very limited because of the toxic side effects ofanticancer drugs. As explained above, side effects results from the factthat the anticancer drugs used in chemotherapy lack efficientselectivity for tumor cells. To suppress the toxic side effects of theanticancer drugs to normal cells and to improve their efficiency towardmalignant cells, lots of studies have been carried out. The preferablemethods are using micelle or microsphere as a carrier of anticancer drugand conjugating anticancer drugs to polymeric carriers.

The first method that uses micelle or microsphere as a carrier ofanticancer drug is to reduce side effects of cancer treatment byinserting anticancer drug into micelle or microsphere and letting itrelease slowly. When anticancer drug is administered separately, itworks in a short period in large quantities, by which side effects arecaused. This method is a good try to reduce those side effects byinducing slow release of the anticancer drug under the condition ofenveloped in micelle or microsphere (Pharm. Res., 1983, 15, 1844).

The second method is to produce anticancer drug-polymer complex bycombining the drug with polymer. Side effects are caused from the factthat the anticancer drugs used in the present cancer chemotherapy lackefficient selectivity for tumor cells. Thus, studies of conjugatinganticancer drugs to polymeric carriers have been carried out as onepromising approach to suppress the side effects of the anticancer drugsto normal cells and to improve their efficiency toward tumor cells.Expected advantageous features of this method are preferable tissuedistribution of drug given by the character of the polymeric carrier,prolonged half-life of drug. in plasma, and controlled drug release fromthe polymeric carrier by adjustment of the chemical properties of thebond between the drug and the carrier.

Several kinds of polymers, naturally occurring and synthetic polymershave been studied as carriers of anticancer drugs. Among naturallyoccurring polymers, immunoglobulins are most widely used as the carrierdue to their high specificity and wide applicability to many kinds oftumor cells. Utility of immunoglobuline as the polymeric carrier is,however, restricted by its chemical and physical properties. Forexample, modification of immunoglobulins by anticancer drugs often leadsto precipitation due to hydrophobicity of the drugs. Furthermore,modification procedures are limited to ones performed in mild conditionsto avoid denaturation of the immunoglobulins during modification.

Recently, the polymeric carrier of the drug can be freely designed usingmany kinds of synthetic polymers available today, and various organicreactions can be used to introduce drug to the synthetic polymericcarrier. From this point of view, several kinds of synthetic polymershave been investigated, such as poly(N-2-(hydroxypropyl)methacrylamide),poly(divinyl ether-co-maleic anhydride), poly(styrene-co-maleicanhydride), dextran, poly(ethylene glycol), poly(L-glutamic acid),poly(aspartic acid) and poly(L-lysine).

Using pathophysiological characteristics of tumor tissues withanticancer drug-polymer complex, cancer can be treated. Generally intumor tissues, more blood vessels are generated than in normal tissuesin order to get enough nutrition for the growth of tumor cells. Theblood vessels in tumor tissues have bigger size than those in normaltissues but their structure is defective. Drainage through a lymphaticduct is also very limited comparing normal tissues. Therefore, polymerseasily permeate into tumor tissues but hardly be excreted from tumortissues. This specific phenomenon showed in tumor tissues is calledenhanced permeability and retention (EPR) effect (Adv. Drug Deliv. Rev.,2000, 65, 271). As one of the treatments using anticancer drug-polymercomplex, the attempt using N-(hygroxypropyl)methacrylamide(HPMA)-anticancer drug complex is under the phase II clinical trial(U.S. Pat. No. 5,037,883 (1991)).

The anticancer drug-polymer complex forming self-aggregates is expectedto have a large diameter, as compared with unbound drug, which is asmall molecule. The polymeric drug having ideal diameter is expected tocirculate in the blood stream without embolization at capillaries, toescape from excretion in kidney, and to permeate into the target cellsthrough blood vessels. And this self-aggregates form is expected to helpprotect the conjugated drug from enzymatic attack in plasma byconcealing the conjugated drug with the polymer.

As a precursor of chitosan, chitin is a natural polymer comprising(1→4)-β -glycoside bond in which N-acethyl-D-glucosamine units arerepeated and is generally found in outer coat of insects includinginvertebrate Crustacea and cell wall of fungi. Chitosan is a basicpolysaccharide generated through N-deacethylation by treating chitinwith the high concentration of alkali. Chitosan has been known to besuperior to other synthetic polymers in cell adsorption capacity,biocompatibility, biodegradability and plasticity.

Thus, the present inventors have synthesized a novel anticancerdrug-chitosan complex having strong points of micelle by makinganticancer drug react with a polymer directly to form self-aggregatesand making the anticancer drug be induced therein, which is differentfrom the way of inserting anticancer drug into micelle. And, the presentinvention has been accomplished by confirming that the anticancerdrug-chitosan complex can release the drug slowly and continuously, andcan be controlled drug release by adjustment of the chemical propertiesof the bond between the drug and the chitosan, resulting in highselectivity against tumor tissues.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an anticancerdrug-chitosan complex forming self-aggregates, which can be effectivelyused for cancer chemotherapy by releasing the drug continuously for along period of time, by enhancing specificity against tumor tissues andby increasing the content of anticancer drug, and the preparation methodthereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The application of the preferred embodiments of the present invention isbest understood with reference to the accompanying drawings, wherein:

FIG. 1 is a graph showing the mean diameter and size distribution ofadriamycin-chitosan complex of the present invention in aqueous solutionmeasured by light scattering;

FIG. 2 is a set of transmission electron microscopy photographs of theadriamycin-chitosan complex of the present invention;

-   -   A: 5×10⁴ magnification (Bar: 200 nm),    -   B: 1×10⁶ magnification (Bar: 50 nm)

FIG. 3 is a graph showing the different releasing level of adriamycinaccording to the pH from the adriamycin-chitosan complex of the presentinvention.

-   -   : pH 4,        : pH 7

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention provides an anticancer drug-chitosan complexforming self-aggregates.

The present invention also provides a preparation method of the aboveanticancer drug-chitosan complex.

Hereinafter, the present invention is described in detail.

The present invention provides an anticancer drug-chitosan complexforming self-aggregates.

In the preferred embodiments of the present invention, every kinds ofchitosan having 10³-10⁶ MW can be used as a carrier of anticancer drug,and soluble chitosan having high biodegradability and biocompatibilityis preferred. Especially, glycol chitosan with enhanced solubility byintroducing glycol group is more preferred. And, most hydrophobicanticancer drugs can be used for the anticancer drug-chitosan complex ofthe present invention, and especially, adriamycin is preferred. Thepreferable size of the anticancer drug-chitosan complex of the presentinvention is 1 nm-2,000 nm. Especially, 10 nm-80 nm is more preferred.

The anticancer drug-chitosan complex of the present invention probablyincludes a linker additionally dissolved in an acidic condition. As alinker, cis-aconitic anhydride, glutaric anhydride, succinic anhydride,oligopeptide and benzoyl hydrazone are can be used, and especially,pH-sensitive cis-aconitic anhydride is preferred (Biochem. Biophys. Res.Comm., 1981, 102, 1048).

The anticancer drug-chitosan complex of the present invention is formingmicelle-like, round-shaped self-aggregates in aqueous media due to theamphiphilicity of the complex by the hydrophobic group of anticancerdrug and the hydrophilic group of chitosan.

The size of anticancer drug-chitosan complex of the present inventionvaries according to the amount of included anticancer drug and thepossible amount of included anticancer drug is 1-70 weight %.

The present inventors used the above anticancer drug-chitosan complex asan anticancer drug carrier, which include the drug forcefully therein.In the preferred embodiment of the present invention, every kind ofhydrophobic anticancer drugs can be used as an anticancer drug.Especially, adriamycin, taxol, cis-platin, mitomycin-C, daunomycin and5-fluorouracil are more preferred. The preferable diameter of anticancerdrug-chitosan complex containing anticancer drug inside is 1 nm-2,000nm, and the range between 10 nm and 800 nm is more preferred.

Inside of anticancer drug-chitosan complex of the present invention iscomposed of hydrophobic anticancer drug and especially some hydrophilicparts of the anticancer drug are combined with chitosan, which causestrong hydrophobicity inside of the complex. Therefore, anticancerdrug-chitosan complex of the present invention provides easy access forhydrophobic anticancer drug to the inside of the complex and couldincrease the amount of the drug. Either the same anticancer drugs can beused for both composing anticancer drug-chitosan complex and beinginserted inside of the complex. And also, many different kinds ofanticancer drugs can be inserted in anticancer drug-chitosan complex alltogether. Owing to the similarity of properties between anticancerdrug-chitosan complex composing material and inserted anticancer drugtherein, this complex has greater effect as a carrier than any othercarrier has.

The anticancer drug-chitosan complex of the present invention has highselectivity against tumor tissues with enhanced permeability andretention (EPR) effect, so that it can be accumulated in tumor tissueswith greater amount to effectively work for target cells, comparing tosmall molecular weight anticancer drugs. The complex is also formingmicelle-like round-shaped self-aggregates in aqueous media, which iscaused by hydrophobic anticancer drug combined with hydrophilic chitosanused as a major chain. Generally, micelle is a round-shaped aggregateformed by molecules having both hydrophobic group and hydrophilic groupin aqueous media. At this time, hydrophilic group is aggregating outsidethe formed aggregate and hydrophobic group is gathering inside (Adv.Drug Deliv. Rev., 1996, 21, 107). This aggregate has been widely used asan carrier of various hydrophobic anticancer drugs. This kind of drugdelivery system using amphiphilic polymer forming self-aggregates showedhigh selectivity against target cells and remarkably reducedcytotoxicity to normal cells. In addition, this system makes the drug beretained long enough and be released slowly and continuously resultingin an effective use for the treatment of serious disease like cancer.

The anticancer drug-chitosan complex of the present invention is ananticancer drug-polymer complex and an anticancer drug carrier havinghigh selectivity against tumor tissues, having various advantages ofmicelle, and having capacity to release the drug continuously.Therefore, the anticancer drug-chitosan complex of the present inventioncan be effectively used as an anticancer drug having a strong anticancereffect.

The present invention also provides a preparation method of the aboveanticancer drug-chitosan complex.

The preparation method of the anticancer drug-chitosan complex of thepresent invention comprises following steps:

-   -   (1) combining hydrophobic anticancer drug with linker        characterized by being dissolved in acidic condition; and    -   (2) combining the complex of anticancer drug and linker with        hydrophilic chitosan.

In the preferred embodiment of the present invention, adriamycin is usedas hydrophobic anticancer drugs. As a linker, cis-aconitic anhydride,glutaric anhydride, succinic anhydride, oligopeptide and benzoylhydrazone are can be used, and especially, pH-sensitive cis-aconiticanhydride is preferred (Biochem. Biophys. Res. Comm., 1981, 102, 1048).

Cis-aconitic anhydride used for the combining anticancer drug withchitosan is a linker which is cut in acidic pH condition and release theanticancer drug. Tumor tissues show lower pH than normal tissues. Thus,this pH-sensitive cis-aconitic anhydride can improve the selectivity ofanticancer drug against tumor tissues, and relieve the cytotoxicity tonormal tissues, which has been the biggest problem of anticancer drugs.

As a hydrophilic chitosan, glycol chitosan wherein glycol group isintroduced is preferred.

The anticancer drug-chitosan complex of the present invention can beprepared by directly combining anticancer drug with chitosan or bylinking anticancer drug to chitosan using a linker; the later ispreferred.

The preparation method of anticancer drug-chitosan complex of thepresent invention includes the loading procedure of the anticancer druginto the inside of anticancer drug-chitosan complex formingself-aggregates.

Adriamycin, taxol, cis-platin, mytomycin-C, daunomycin and5-fluorouracil are the examples of anticancer drug to be loaded into theinside of anticancer drug-chitosan complex. Loading by chemical bondingis limited to 10% at best, however, by the physical loading, the loadingquantity of anticancer drug can be enhanced up to 60%, resulting in theincrease of anticancer drug contents over the limitation of chemicalbonding.

EXAMPLES

Practical and presently preferred embodiments of the present inventionare illustrative as shown in the following Examples.

However, it will be appreciated that those skilled in the art, onconsideration of this disclosure, may make modifications andimprovements within the spirit and scope of the present invention.

Example 1 Preparation of Adriamycin-Chitosan Complex 1

<1-1> Preparation of cis-aconityl adriamycin

In order to prepare cis-aconityl adriamycin, the present inventorsdissolved 13.46 mg of cis-aconitic anhydride (Chemical Formula 2) in 0.5ml of dioxane and then dissolved 10 mg of adriamycin (ChemicalFormula 1) in 350 μl of pyridine. After then, the present inventorsadded the cis-aconityl solution into adriamycin solution and let it bereacted at 4° C. or 24 hours.

The above reaction mixture was scattered into 5 ml of chloroform and 5%NaHCO₃ solution, and stirred strongly. Then, chloroform layer in thebottom was removed and the rest solution was extracted with ethylacetate, after which solvent was evaporated, resulting in thepreparation of cis-aconityl adriamycin. The reaction procedure issummarized in the <Reaction Formula 1>.

<1-2> Preparation of chitosan complex

Glycol chitosan was dissolved in 10 ml of water at the concentration of1 W % and then 10 ml of methanol was added thereto. 3 mg of cis-aconityladriamycin was dissolved in 1 ml of DMF, which was slowly loaded intoglycol chitosan solution. 7 mg of 1-ethyl-3-(3-dimethyl-aminopropyl)carbodiimide (EDC) and 5 mg of N-hydrosuccinimide (NHS) were dissolvedin 1 ml of methanol, which was added into the reaction mixture andstirred at room temperature for 24 hours. The reaction mixture wasdialyzed for 2 days to remove the unreacted cis-aconityl adriamycin andthen freeze-dried, resulting in the preparation of adriamycin-chitosancomplex of the present invention (FIGS. 1 and 2). The above reactionprocedure was summarized in the following <Reaction Formula 2>.

Example 2 Preparation of adriamycin-chitosan Complex 2

During the reaction process between cis-aconityl adriamycin and glycolchitosan, 2 mg of cis-aconityl adriamycin was dissolved in 1 ml of DMF,which was slowly loaded into glycol chitosan solution. After then, 4.6mg of EDC and 3.3 mg of NHS were dissolved in 1 ml of methanol, whichwas added into the above reaction mixture. The same method as the above<1-2>was performed for the rest of the procedure to prepareadriamycin-chitosan complex of the present invention.

Example 3 Preparation of adriamycin-chitosan Complex 3

During the reaction process between cis-aconityl adriamycin and glycolchitosan, 1 mg of cis-aconityl adriamycin was dissolved in 1 ml of DMF,which was slowly loaded into glycol chitosan solution. After then, 2.3mg of EDC and 1.7 mg of NHS were dissolved in 1 ml of methanol, whichwas added into the above reaction mixture. The same method as the above<1-2>was performed for the rest of the procedure to prepareadriamycin-chitosan complex of the present invention.

Example 4 Preparation of adriamycin-chitosan Complex 4

During the reaction process between cis-aconityl adriamycin and glycolchitosan, 4 mg of cis-aconityl adriamycin was dissolved in 1 ml of DMF,which was slowly loaded into glycol chitosan solution. After then, 9.3mg of EDC and 6.7 mg of NHS were dissolved in 1 ml of methanol, whichwas added into the above reaction mixture. The same method as the above<1-2> was performed for the rest of the procedure to prepareadriamycin-chitosan complex of the present invention.

Example 5 Preparation of adriamycin-chitosan Complex 5

During the reaction process between cis-aconityl adriamycin and glycolchitosan, 5 mg of cis-aconityl adriamycin was dissolved in 1 ml of DMF,which was slowly loaded into glycol chitosan solution. After then, 11.7mg of EDC and 8.3 mg of NHS were dissolved in 1 ml of methanol, whichwas added into the above reaction mixture. The same method as the above<1-2> was performed for the rest of the procedure to prepareadriamycin-chitosan complex of the present invention.

As shown in the above Example 1-Example 5, the amount of adriamycincontained in adriamycin-chitosan complex depends on the amount ofcis-aconityl adriamycin.

Example 6 Preparation of adriamycin-chitosan Complex 6

Cis-aconityl adriamycin and glycol chitosan were reacted for 6 hours.And, the same method as the above <1-2> was performed for the rest ofthe procedure to prepare adriamycin-chitosan complex of the presentinvention.

Example 7 Preparation of adriamycin-chitosan Complex 7

Cis-aconityl adriamycin and glycol chitosan were reacted for 12 hours.And, the same method as the above <1-2> was performed for the rest ofthe procedure to prepare adriamycin-chitosan complex of the presentinvention.

Example 8 Preparation of adriamycin-chitosan Complex 8

Cis-aconityl adriamycin and glycol chitosan were reacted for 18 hours.And, the same method as the above <1-2> was performed for the rest ofthe procedure to prepare adriamycin-chitosan complex of the presentinvention.

Example 9 Preparation of adriamycin-chitosan Complex 9

Cis-aconityl adriamycin and glycol chitosan were reacted for 48 hours.And, the same method as the above <1-2> was performed for the rest ofthe procedure to prepare adriamycin-chitosan complex of the presentinvention.

As shown in the above Example 6-Example 9, the amount of adriamycincontained in adriamycin-chitosan complex depends on the reaction timebetween cis-aconityl adriamycin and glycol chitosan.

Example 10 Preparation of adriamycin-chitosan Complex FormingSelf-Aggregates Containing adriamycin Therein 1

In order to prepare adriamycin-chitosan complex forming self-aggregatescontaining adriamycin inside, the present inventors dissolved 1 mg ofadriamycin in 1 ml chloroform solution and then added triethylaminethereto. 5 mg of adriamycin-chitosan complex of the present inventionwas dissolved in 10 ml of water, and then the above adriamycin solutionwas slowed loaded thereto, followed by 24 hours stirring. At this time,let the vessel opened and contacted air for the evaporation of addedchloroform. 24 hours later, ultrafiltration was performed for everysolution with molecular weight cut-off (MWCO) 1000 filter in order toeliminate remaining adriamycin which didn't permeate into the inside ofadriamycin-chitosan complex. The gathered materials on the filter weredissolved in required amount of water again and then freeze-dried,resulting in the preparation of adriamycin-chitosan complex containingadriamycin inside (Table 1). In the Table 1, the loading effectrepresents the actual amount of loaded adriamycin in adriamycin-chitosancomplex by %.

TABLE 1 Adriamycin- chitosan Amount of Loading complex/water Adriamycinloading effect (mg/ml) (mg) (w/w %) (%) 5 mg/10 ml 1 mg 18.9 W % 94.33%5 mg/10 ml 2 mg 38.9 W % 97.23%

Example 11 Preparation of adriamycin-chitosan Complex FormingSelf-Aggregates Containing adriamycin Therein 2

The present inventors dissolved 1 mg of adriamycin in 1 ml chloroformsolution. And, the same method as the above Example 10 was performed forthe rest of the procedure to prepare adriamycin-chitosan complex formingself-aggregates containing adriamycin therein (Table 1).

Example 12 Preparation of adriamycin-chitosan Complex FormingSelf-Aggregates Containing Taxol Therein 1

1 mg of taxol was dissolved in 1 ml DMF in order to prepareadriamycin-chitosan complex containing taxol inside. 5 mg ofadriamycin-chitosan complex of the present invention was dissolved in 10ml of water, and then the above taxol solution was slowly loadedthereto, followed by 24 hours stirring. 24 hours later, dialysis wasperformed for every solution with a MWCO 3500 membrane for 2 days inorder to eliminate remaining taxol which didn't permeate into the insideof adriamycin-chitosan complex. After the dialysis, the solution wasfreeze-dried, resulting in the preparation of adriamycin-chitosancomplex containing taxol therein.

Example 13 Preparation of adriamycin-chitosan Complex FormingSelf-Aggregates Containing Taxol Therein 2

The present inventors dissolved 2 mg of taxol in 1 ml of DMF. And, thesame method as the above Example 12 was performed for the rest of theprocedure to prepare adriamycin-chitosan complex forming self-aggregatescontaining taxol therein.

Experimental Example 1 Measurement of Released adriamycin fromadriamycin-chitosan Complex According to pH

The present inventors have observed the releasing level of adriamycinaccording to the pH from the adriamycin-chitosan complex of the presentinvention. Particularly, adriamycin-chitosan complex was dispersed intowater until the concentration reached at 2 mg/ml, and then 500 μl ofadriamycin-chitosan complex solution was enveloped in cellulose dialysismembrane (MWCO 12,000-14,000). After soaking thereof in each pH 4 and pH7 water, the present inventors stirred thereof at 37° C. with 150 rpmand obtained releasing solution according to the time-table to measurethe amount of released adriamycin with a spectrophotometer.

As a result, as shown in FIG. 3, the amount of released adriamycin wasgradually increased in both cases of pH 4 and pH 7 as time went by. Butwhen being soaked in pH 4 water solution, the adriamycin-chitosancomplex of the present invention released much more adriamycincomparatively, suggesting that the adriamycin-chitosan complex can beeffectively used for the treatment of cancer by releasing adriamycinproperly to the tumor-growing area which shows generally acidiccondition.

INDUSTRIAL APPLICABILITY

As shown above, the anticancer drug-chitosan complex of the presentinvention has prolonged drug-releasing time by forming self-aggregates,enhanced selectivity against tumor tissues, and increase the amount ofdrug by adding the anticancer drug into the inside of self-aggregatesphysically. Therefore, the anticancer drug-chitosan complex of thepresent invention can be effectively used for cancer chemotherapy.

Those skilled in the art will appreciate that the conceptions andspecific embodiments disclosed in the foregoing description may bereadily utilized as a basis for modifying or designing other embodimentsfor carrying out the same purposes of the present invention. Thoseskilled in the art will also appreciate that such equivalent embodimentsdo not depart from the spirit and scope of the invention as set forth inthe appended claims.

1. An anticancer drug-chitosan conjugate comprising: an adriamycin; anda hydrophilic glycol chitosan, wherein the adriamycin is bonded to theglycol chitosan via a linker which degrades in an acidic condition, andwherein the conjugate self-aggregates in an aqueous media.
 2. Theanticancer drug-chitosan conjugate as set forth in claim 1, wherein thecontent of the adriamycin ranges from 1 to 70 weight %.
 3. Theanticancer drug-chitosan conjugate as set forth in claim 1, wherein themean molecular weight of the chitosan is 10³˜10⁶dalton.
 4. Theanticancer drug-chitosan conjugate as set forth in claim 1, wherein thelinker is selected from the group consisting of cis-aconitic anhydride,benzoyl hydrazone, and oligopeptide and wherein the adriamycin is bondedto the glycol chitosan via the linker which degrades in an acidiccondition.
 5. The anticancer drug-chitosan conjugate as set forth inclaim 1, wherein the diameter of the self-aggregated complex is 10˜800nm.
 6. The anticancer drug-chitosan conjugate as set forth in claim 1,wherein a hydrophobic anticancer drug is further loaded inside theself-aggregates.
 7. The anticancer drug-chitosan conjugate as set forthin claim 6, wherein the hydrophobic anticancer drug is selected from thegroup consisting of adriamycin, taxol, cis-platin, daunomycin and5-fluorouracil.